The simple fact is that people don't want the immense responsibility that logically pertains to their voluntary actions actions, so they fabricate denials of reality as a convenient escape, out of pure selfishness-- like every other atrocity in history.   The study of law includes an analysis of how people excuse their wrongdoings, fabricating pausible rationalizations for their acting to benefit at another's expense; denial is typically the first of these, claiming that the act "does not hurt anyone," however obvious the contrary. Other rationales follow, such as self-preservation, natural right to act, and eventually growing defensive by blaming the victim.   While the fabricator typically believes his story original, it is anything but-- it's simply the inevitable course of selfishness.
Label: Non-Sarcastic